Orion ATLAS EQ-G User Manual download pdf (Page 6)

Polar Alignment

For Northern Hemisphere observers, approximate polar align-

ment is achieved by pointing the mount’s right ascension axis

at the North Star, or Polaris. It lies within 1° of the north celes-

tial pole (NCP), which is an extension of the Earth’s rotational

axis out into space. Stars in the Northern Hemisphere appear

to revolve around the NCP.

To find Polaris in the sky, look north and locate the pattern

of the Big Dipper (Figure 6). The two stars at the end of the

“bowl” of the Big Dipper point right to Polaris.

Observers in the Southern Hemisphere aren’t so fortunate to

have a bright star so near the south celestial pole (SCP). The

star Sigma Octantis lies about 1° from the SCP, but it is barely

visible with the naked eye (magnitude 5.5).

For general visual observation, an approximate polar align-

ment is sufficient.

1. Level the equatorial mount by adjusting the length of the

three tripod legs.

2. There are two latitude adjustment L-bolts (see Figure 5);

loosen one while tightening the other. By doing this you

will adjust the latitude of the mount. Continue adjusting the

mount until the pointer on the latitude scale is set at the

latitude of your observing site. If you don’t know your lati-

tude, consult a geographical atlas to find it. For example,

if your latitude is 35° North, set the pointer to 35. The lati-

tude setting should not have to be adjusted again unless

you move to a different viewing location some distance

away.

3. Loosen the Dec. lock lever and rotate the telescope’s opti-

cal tube until it is parallel with the right ascension axis, as

it is in Figure 5.

4. Move the tripod so the telescope tube and right ascen-

sion axis point roughly at Polaris. If you cannot see Polaris

directly from your observing site, consult a compass and

rotate the tripod so the telescope points north.

The equatorial mount is now polar aligned for casual observ-

ing. More precise polar alignment is recommended for

astrophotography. For this we recommend using the polar

axis finder scope.

From this point on in your observing session, you should not

make any further adjustments to the latitude of the mount,

nor should you move the tripod. Doing so will undo the polar

alignment. The telescope should be moved only about its R.A.

and Dec. axes.

The Polar Axis Finder Scope

The Atlas EQ-G mount comes with a polar axis finder scope

(Figure 7) housed inside the right ascension axis of the

mount. When properly aligned and used, it makes accurate

polar alignment quick and easy to do. Unthread the cover at

the rear of the mount’s right ascension axis and remove the

cap on the front opening of the equatorial mount (Figure 5) to

view through the polar axis finder scope.

Alignment of the Polar Axis Finder Scope

1. Loosen the Dec. lock lever and rotate the optical tube about

the declination axis until you have a clear view through the

polar axis finder scope (Figure 8). Tighten the Dec. lock

lever.

2. Look through the polar finder at a distant object (during

the day) and center it in the crosshairs. You may need to

adjust the latitude adjustment L-bolts and the tripod posi-

tion to do this. Focus the polar finder by rotating the eye-

piece.

3. Rotate the mount 180° about the R.A. axis. It may be con-

venient to remove the counterweights and optical tube

before doing this.

4. Look through the polar finder again. Is the object being

viewed still centered on the crosshairs? If it is, then no

further adjustment is necessary. If not, then look through

the polar finder while rotating the mount about the R.A.

axis. You will notice that the object you have previously

centered moves in a circular path. Use the three alignment

set-screws on the polar axis finder (Figure 7) to redirect

the crosshairs of the polar finder to the apparent center of

this circular path.

5. Repeat this procedure until the position that the crosshairs

point to does not rotate off-center when the mount is rotat-

ed in R.A.

Figure 8. The optical tube must be rotated about the declination

axis in order to view through the polar axis finder.

Figure 7. The polar axis finder scope.

Eyepiece

focus ring

Alignment

setscrew (3)

Focus

lock ring

Objective

lens

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Orion ATLAS EQ-G User Manual Page 6

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